Functional Magnetic Resonance Imaging of ATP Cough in Chronic Cough Patients

June 10, 2022 updated by: Stuart Mazzone

A Functional Magnetic Resonance Imaging Study to Investigate ATP-sensitive Cough Neural Pathways in Patients With Chronic Cough Hypersensitivity

Persistent cough is a distressing symptom for people with respiratory disorders. Patients also often experience an ongoing urge-to-cough that prompts coughing, and which fails to resolve the sensation. Understanding how the brain controls cough and the urge-to-cough could lead to new cough suppressing therapies. The overall objective of this project is to use functional brain imaging (fMRI) to identify brain regions that are involved in the exaggerated urge-to-cough in humans with chronic cough. Our focus will be on the brainstem where information from the airways first arrives in the central nervous system.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

Peripheral effects of ATP via P2X3 receptors

ATP has been shown to be a tussive agent particularly on chronic cough patients who were more sensitive than non-cough subjects to inhaled ATP. ATP has been shown to augment the cough response to capsaicin in patients with asthma. Gefapixant at a single oral dose of 50 mg did not modulate capsaicin cough responses in normal volunteers and chronic cough subjects while inhibiting ATP-induced cough particularly in chronic cough subjects. These observations would suggest that ATP has a direct effect on a subset sensory neurons that evoke coughing through the activation of P2X3 receptors.

The use of fMRI to provide insights into the peripheral and central sites of activation by ATP/P2X3 activation We have generated functional brain imaging (fMRI) data to suggest that the different brain circuits in receipt of nodose and jugular ganglia neuron inputs (as identified in animal studies) are conserved in humans. When inhaled, the tussigenic compound capsaicin (from hot chili peppers) indiscriminately stimulates both nodose and jugular chemosensitive afferents and we have published that capsaicin inhalation produces brain activations in the primary sensory, anterior and mid-insula, cingulate, premotor, motor and orbitofrontal cortices. These regions are presumed to encode perceptual awareness of airway irritation, and the associated emotional, cognitive and behavioral (motor) consequences. For example, activity in the human primary sensory cortex (which receives jugular ganglia inputs in animal studies) correlates with an individual's perception of airway irritation (their perceived need/ urge to cough) while activity in the insula (in receipt of nodose inputs) relates closely to the actual magnitude of the delivered stimulus independent of perception. We have now built upon these published findings by using high resolution brainstem fMRI during the inhalation of ATP (expected to only activate P2X2/3 expressing nodose-derived airway afferents) versus capsaicin (expected to activate both jugular and nodose chemosensitive afferents). Our results are striking and reveal that ATP inhalation evokes an in increased signal level in the brainstem regions corresponding to the nTS, while capsaicin inhalation produces activations in both the nTS and in an area of the dorsal spinal trigeminal nucleus on the lateral margins of the brainstem that contains the paratrigeminal nucleus. Indeed, our healthy participants did not cough as much to ATP compared to capsaicin, consistent with studies cough in animals and humans and the relatively poor cough-evoking properties of ATP in healthy humans. However, the perception of airway irritation was identical between ATP and capsaicin stimuli. We believe that cough production will ultimately be dependent upon activation of the neural circuit that integrates in the paratrigeminal nucleus (i.e.' the jugular afferent pathway) and therefore we hypothesize that there is an upregulation of the capacity of ATP to act via jugular ganglia pathways in chronic cough patients.

The fMRI studies described above provide an exciting opportunity to assess for the first time which primary airway afferent pathways are likely excited or sensitized by ATP and, in turn, what aspects of the central processing of airway sensory information is altered by ATP. We have reported previously that patients with chronic cough display functional brain responses consistent with a state of central sensitization that closely resembles the central sensitization accompanying chronic pain.

We will extend upon these findings by determining whether ATP-sensitive pathways in the brainstem and brain are altered in patients with chronic cough, and in doing so provide insight into whether ATP effects vagal afferent processing through an interaction with nodose and/ or jugular neural pathways.

Study Type

Interventional

Enrollment (Actual)

58

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Australia
    • Victoria
      • Parkville, Victoria, Australia, 3010
        • The University of Melbourne

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years and older (Adult, Older Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Description

Inclusion Criteria:

  • Patients with physician diagnosed chronic refractory cough (cough lasting >8 weeks).
  • > 18 years of age
  • Must be cognitively impaired

Exclusion Criteria:

  • People with contraindications to MRI scanning (i.e. metal implants, claustrophobia).
  • History of uncontrolled asthma or chronic respiratory disease (other than refractory cough).
  • Evidence of an allergic reaction to capsaicin (chilli).
  • Pregnant women.
  • Smoking, current or recent history (last 6 months).

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Basic Science
  • Allocation: Non-Randomized
  • Interventional Model: Parallel Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Chronic cough participant

Twenty-five (25) Idiopathic chronic cough patients, defined as refractory to disease modifying therapies (eg anti-asthma medications), will be recruited.

Participants will attend two sessions. In the first they will inhale in a single breath a nebulized solutions of increasing doses of Adenosine Triphosphate (ATP; 0.2-300 microM) and capsaicin (0.5-125 microM) to determine their individual cough and urge-to-cough thresholds. In the second session, participants will undergo functional brain imaging (fMRI) for 1 hour while inhaling over 24 seconds randomly administered nebulized solutions of saline, or threshold doses of ATP or capsaicin.
Drug: Adenosine Triphosphate
Participants will inhale escalating concentrations of Adenosine Triphosphate (ATP) to induce cough and the urge-to-cough
Other Names:
  • ATP
Drug: Capsaicin
Participants will inhale escalating concentrations of capsaicin to induce cough and the urge-to-cough
Other: Functional Brain Imaging
Participants will have scans of their brain activity using 3 Tesla (3T) brainstem restricted functional brain imaging (fMRI)
Other Names:
  • fMRI
Experimental: Healthy control participant

Twenty-five (25) appropriately age and sex matched healthy non-smoking individuals will be recruited as the comparison group.

Participants will attend two sessions. In the first they will inhale in a single breath a nebulized solutions of increasing doses of ATP (0.2-300 microM) and capsaicin (0.5-125 microM) to determine their individual cough and urge-to-cough thresholds. In the second session, participants will undergo fMRI for 1 hour while inhaling over 24 seconds randomly administered nebulized solutions of saline, or threshold doses of ATP or capsaicin.
Drug: Adenosine Triphosphate
Participants will inhale escalating concentrations of Adenosine Triphosphate (ATP) to induce cough and the urge-to-cough
Other Names:
  • ATP
Drug: Capsaicin
Participants will inhale escalating concentrations of capsaicin to induce cough and the urge-to-cough
Other: Functional Brain Imaging
Participants will have scans of their brain activity using 3 Tesla (3T) brainstem restricted functional brain imaging (fMRI)
Other Names:
  • fMRI

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Brainstem neural activations
Time Frame: 18 months
fMRI will be used to determine the location and magnitude of neural responses in the brain during ATP and capsaicin inhalation. fMRI non-invasively measures Blood Oxygen Level Dependent (BOLD) signals in the brain which can be used to identify regions of the brain that increase activity associated with the inhaled stimuli. Comparisons between regional BOLD responses evoked by ATP and capsaicin (compared to saline) will allow the different neural networks involved in cough generation to be explored in healthy and chronic cough participants.
18 months

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Behavioral responses
Time Frame: 18 months
Participant responses (cough and the urge-to-cough) evoked by ATP and capsaicin will be measured by counting audible coughs and by asking participants to rate their perception of urge-to-cough using visual analogue scales (VAS).
18 months

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Stuart Mazzone

Collaborators

Imperial College London
Monash University
Queen's University, Belfast

Investigators

  • Principal Investigator: Stuart Mazzone, PhD, University of Melbourne

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

March 1, 2019

Primary Completion (Actual)

May 13, 2022

Study Completion (Actual)

May 13, 2022

Study Registration Dates

First Submitted

October 24, 2018

First Submitted That Met QC Criteria

October 25, 2018

First Posted (Actual)

October 29, 2018

Study Record Updates

Last Update Posted (Actual)

June 15, 2022

Last Update Submitted That Met QC Criteria

June 10, 2022

Last Verified

June 1, 2022

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • Study 58136

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

No

IPD Plan Description

IPD will not be shared

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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